The "Defining" skill: Neuter Instrumental ending

I think the explanation might not be 100% correct about how the Instrumental ending for neuter nouns works.

It's written as "When it comes to neuter nouns, you have to delete the final -o and replace it with -iem."
But if I remember correctly, the new ending is "em" not "iem" and the additional "i" is only there after certain letters (like "k" and "g").

If I remember wrong (it has been a while since I attempted to understand the polish grammar) I apologize.

Also thank you so much for all the work you put into this. It's great to be able to learn Polish here!